


Quirks and Dying Will Flames

by Kc_chi



Category: Katekyou Hitman Reborn!, 僕のヒーローアカデミア | Boku no Hero Academia | My Hero Academia
Genre: Crossover, possibly ooc characters
Language: English
Status: In-Progress
Published: 2020-12-27
Updated: 2020-12-28
Packaged: 2021-03-10 16:40:08
Rating: Not Rated
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 6
Words: 8,150
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/28370280
Author URL: https://archiveofourown.org/users/Kc_chi/pseuds/Kc_chi
Summary: Tsuna, after a long battle, dies and wakes up in the infirmary of UA.Blinking away the slight migraine and grogginess that seemed to form, Tsuna tilts his head at the detective. "What's a quirk?......"Updates whenever motivation doesn't swing a sledgehammer at me and leaves.
Comments: 21
Kudos: 202





	1. Chapter 1

**Author's Note:**

> Crossover between My hero Academia and Katekyo Hitman Reborn!
> 
> Characters might be OOC since it's been a while since I've watched both animes. But anywho, join Tsuna as he lives a new life in the my hero academia universe. :)

The sound of a gunshot echoing through the clearing of the forest was heard, then silence once again reigned.

The person who held the gun, slowly let his outstretched arm fall back to his side, grunting as his other arm wrapped around his torso. Blood seeping through the ripped fabric and dripping down onto the blood stained grass.

He laughed dryly as he slumped to his knees, blood dripping down his chin as he coughed.

Heaving and eyes threatening to close, he slowly looked around the carnage. Bodies of allies and enemies alike littered the clearings grounds.

He grit his teeth as tears flowed down his cheeks, "I'm sorry, everyone......."

He forced his legs to work, getting up slowly as he made his way to a wrecked fedora with an orange band barely wrapping around it. The stitching coming undone as he carefully picked it up and cradled it to his chest.

A broken sob made its way out as he slid down a tree, the bark scratching and tearing up the already ripped black suit he donned.

"I'm sorry.........." He whispered as his eyes closed, his hands keeping a vice tight grip onto the hat as he breathed his last.

The soft beeping of a heart monitor was heard as his eyes slowly fluttered open. The bright lights making him squint as his eyes adjusted to sudden change.

He stared at the ceiling for a few seconds before moving his head to look at his side, where he spotted the heart monitor as well as a table where a glass filled with water sat on a tray.

He blinked and carefully propped up using his elbow, grimacing at the soreness that spread throughout his body.

"You're awake!" A voice startled him in his quest to sit up, making him abruptly turn his head to stare at a figure who sat on the other side of the room.

"Ugh!...." He plopped back down onto the bed, unable to hold his weight as his arms gave up and his head throbbed at the abrupt movement.

"You better lie down for now. I'm sure you're body is pretty shocked at dropping down from unbelievable heights and getting manhandled by heroes in training, which needs to be addressed so they don't end up just tossing civilians in missions." She grumbled the last part mostly to her self as she made her way towards the bed.

"What?........" He asked in slight disbelief as he attempted to get up a second time.

"What did I just say?!" The other scolded.

The man assessed his surroundings before looking back at the other who now stood in front of him. 

She was quite a short old woman who had a pink helmet on with a purple visor, she wore a lab coat that dragged a little at the floor as she walked. A large syringe she used as a cane and another smaller one holding her hair up in a bun.

He stared in fascination at the odd outfit before looking away, straitening himself as he leaned against the headboard. "Where.... Where am I?......" He registered he was in some sort of infirmary, by the white walls, hospital beds, and equipment that he saw.

She huffed as she grabbed the water filled cup, shoving it to the patient. He carefully took it, saying thanks before taking small sips.

"You're in the infirmary of UA. The students brought you here after they managed to catch you when you decided to skydive without a parachute, unconscious might I add." She raised a brow as he spluttered, coughing out water and gaping at her.

"What?.......... I-.. I was supposed to be dead...." He nervously said as he tried to think of what happened.

"What?" It was now her turn to ask that as her expression turned grim.

Realizing his mistake he nervously chuckled and slowly looked away.

She stared at the man for a few more seconds before marching up to her desk and pulling out a phone.

He distracted himself from the call by looking at his surroundings. A door that he presumed led outside the infirmary was opened a few minutes later confirming his thoughts.

Three others entered the room. A man with unruly black hair, a gray scarf that wrapped around many times sat on his shoulders, his eyes sporting eye bags that made him look like he had not slept in weeks, and a scar that sat beneath his left eye. Another man who looked lanky and would fall over with a gentle breeze stepped in after the first. A mop of messy blonde hair sat atop his head, with long jagged fringes framing his face. The next made him blink in surprise. It was a mouse?.... A bear?.... Wearing a suit.

He stared at the newcomers with fascination and a bit of wariness as his intuition said not to underestimate any of them. Despite their looks, he knew they could probably hold their ground.

"You're awake! We were notified by Recovery girl!" The mouse declared as he sat on the dark haired one's shoulder.

"Yes?..…." He answered warily as he eyed the the animal that talked. Used to such weirdness that occurs on a daily basis, he simply accepted whatever that gets thrown his way by now.

His reaction to their fellow staff had them perk up. Most who see the Principal Nedzu had more of a reaction than this.

"We're here to ask you a few questions, if you don't mind." The blonde proposed as he took a seat on a spare chair. The other following his lead.

"It's alright." He unconsciously straightened up his hunched over position on the bed, as he gently smiled at the other room's occupants.

"I'm Nedzu, the principal of UA, the school infirmary you're in right now!" The mouse, bear, spoke.

"Aizawa Shota..." The dark haired muttered, as he eyed the guest who sat on the bed.

"Toshinori Yagi." The blonde introduced himself.

"You can call me Recovery girl or Shuzenji." The old woman walked up to him, grabbing the now empty glass and placing it onto the the table.

"I'm Tsunayoshi Sawada, pleased to meet you." He smiled.

"Tsunayoshi-san then?" Nedzu asked.

"Oh, just Tsuna is fine, Nedzu-san." 

"Then you may call me just Nedzu as well." He paused, seeing the other give a nod. 

"A friend of mine will be here in a bit to ask some questions." And just as Aizawa said that, a man wearing a brown coat opened the door and walked through. Taking his similar brown hat off as he gave a nod to the others.

"I'm Detective Naomasa Tsukauchi, I was called here to ask a few questions." He stated as he grabbed a chair and situated himself in front of the bed the other layed on.

"Yes." Tsuna nodded as his intuition didn't react, deeming it safe to answer.

"Alright, but I'll warn you, my quirk is detecting lies, and mostly works like a lie detector, so we would know if you're telling the truth." The detective declared. "Any questions before we start?"

"Yes......."  
Blinking away the slight migraine and grogginess that seemed to form, Tsuna tilts his head at the detective. "What's a quirk?......"

The rooms occupants, other than Tsuna seemed to freeze at that question, staring wide eyed at the enigma placed before them.

"What?......" The detective asked, slight suspicion in his features.

"Wha- What's a quirk?....." Tsuna asked again, this time with uncertainty as he took in the reactions of the others in the room with him, as well as slightly wincing at the stutter in his words at the beginning. "Reborn is so gonna put a bullet through my head for that...." He thought.

"Amnesia?.... A memory altering quirk?.." Aizawa suggested at the others.

The detective took a large breath before asking, "What do you remember before you came here?"

"I......I remember dying......" Tsuna solemnly looked down at his lap, his hands clenched around the bunched up fabric of the white blanket on his lap.

Sharp intakes of breath were heard as they stared at the spiky brown haired male, who now had a slight realization in his eyes as he perked up and looked around the room, surveying like he's looking for something.

Recovery girl calmed down first as she realized what the other was doing, standing up from her chair as she pulled out a fedora from her desk, the brunette perking up at seeing the object.

She handed the hat back to the presumed owner. Tsuna taking the hat and smiling sadly, the expression observed by the staff.

"I fixed it up, it was completely battered when you came, you also would not let go of it. Had a hard time getting it out of your clutches." She gently flicked the brunette's forehead.

Tsuna smiled gratefully at the older woman, giving her a blinding smile as he clutched the fixed fedora to his chest. "Thank you." He whispered.

She huffed as she reclaimed her spot on her chair.

"Would- would you like to continue?..." The detective suggested as he stared at the brunette who smiled in return as he gently placed the hat on his lap.

"Yes. I-... We were fighting.... We were ambushed.... We........died......... I'm sure of it.... So how am I here?..." Tsuna recalled the events leading up to the fight, it was supposed to be a day out for the family. They were just going on a small picnic. Then enemies rained down on them and the picnic spot soon became a battlefield. It was supposed to be a break, "Some break that was..." He sarcastically thought.

The UA's staff held grim expressions at that as they turned to the detective who had his lips in a thin line as he nodded. The others immediately straightening at the gesture.

"You died?..." Tsukauchi carefully asked as he eyed the other.

"I did....." Tsuna blinked then shuffled as he raised the slightly torn suit, displaying his front for the others to see.

The UA's staff flinching and staring wide eyed at the scars marring his torso. "He's got more scars than the problem children combined?!" Aizawa buried his expression into his capture scarf. 

"Huh?......" Tsuna stared at where the gunshot wound that killed him should be at, expecting bleeding and a wide open hole. What he saw was, red, irritated skin around a new scar.

"That was pretty bad, brat!" Recovery girl commented, "The bullet was jostled and moved around it was a pain to get out." 

Tsuna sheepishly scratched his cheek as he nervously chuckled. "Haha?....."

"Don't 'Haha' me! You were fighting for who knows how long with a dire injury!!" Recovery girl pointed at the brunette, scolding him for reckless behavior.

"I think it was..... afternoon until the morning of the next day?...." Tsuna tilted his head as he tried to recall how long they were fighting. The time a blur to him, as all of them just focused on getting to safety and surviving. Didn't work out so well....

"WHAT?!?!?" Everyone exclaimed at the brunette's words.

"Fucking brat!! You should be glad you're alive!!!!" Recovery girl swat her syringe cane at him, Tsuna giggling as he put out his hands to stop the onslaught.

Everyone calmed down enough so the investigation could continue, Detective Tsukauchi sighing and running a shaky hand through his hair before asking a question. "You asked what 'quirks' are, do you really not know?"

"Yeah......is it similar to quirky? Like an unexpected or peculiar trait?...." Tsuna carefully trudged as he saw the looks he was getting from the people in the room. "Um....."

"Kind of, yes. But to put in simpler terms, its a superpower that manifests at the age of four and first manifested as a luminescent baby in China." The principal explained.

"Oh?" Tsuna blinked, "There are superpowers? Everyone has them?" He asked, interested in the topic.

"Not everyone, twenty percent of the population don't have them, they are either the people of the older generations or the rare occurrence a quirkless child, born without a quirk." Aizawa sighed as he realized this is more work than he thought.

"That's like the opposite of where I'm from." Tsuna giggled slightly as he took in the new revelation, but suddenly paused as he realized his mistake. "Oh god- The vindice-" Tsuna thought and slightly panicked at that.

"The opposite? That means quirks are a minority from where you come from?" Nedzu inquiring more as he was interested.

Tsuna twiddled his fingers for a minute, seeming to hesitate on answering, "Not exactly......." Taking a deep breath as he concluded that disclosing a bit of information on flames should be alright as long as he doesn't blabber about it all.

"We don't have 'quirks' as what you would call it, its more like an Aura that a small percentage of people can pull through and emerge." Tsuna explained.

"Oh? And what does this 'Aura' do?" Nedzu leaned closer, more interested by the minute, making Aizawa cringe.

"There are different kinds, and different colors. There is the Sky Branch, where, like the name, comes in names of the weather and such, and then there is the Earth Branch where it comes from the earth, like mountains and such." Tsuna sucked in a breath, hoping and silently crying inside that this isn't too much information or the Vindice will have his head. "Dying two times seems fine at this point...." Tsuna grimaced as he sighed.

"I haven't heard of quirks at all up until now.."

Nedzu beamed at that and slowly explained, "Like I said before, its somewhat of a superpower and can range between changing the color of your hair, to making the weather change with a single punch." 

Tsuna's eyes widening at that.

"Some have 'mutant quirks' where the quirk changes the body permanently and is the least common of the three. Transformation quirks are just like the name implies, the user can transform a body part or the whole body into something else temporarily. And the last is the Emitter type quirks, where it allows the user to alter, control, or possibly generate certain things in certain ways." Nedzu continued.

"Oh wow......" Tsuna gaped at the information. "I think.....I'm not in my world anymore......" He timidly chuckled.

"Hah?!" The other staff raising a brow at the brunette's proposition.

"I would have definitely heard of quirks then, even if Namimori is small and kind of isolated, knowledge about quirks would definitely reach us. Almost everyone in the entire world is normal and don't even know they have these 'Aura's', so quirks are not a thing....." Tsuna muttered, reminding Aizawa of a certain problem child in his class.

"Then that concludes it! Tsuna here, is from another universe!" Nedzu declared as he clapped his paws.

"The fuc- How did you come to that conclusion?!" Aizawa sweared.

"Detective?" Yagi turns to the the detective expecting something that diverges from that exclamation, anything.

Tsukauchi sighs, shaking his head as he rubbed his temples, Yagi deflating in his chair as blood trickled down his chin. 

Aizawa groans and drags a hand down his face.

Nedzu cackles as he said, "Alright! For now, you need to rest Tsuna-kun. Your body is quite weak due to Recovery Girl's quirk. We shall continue tomorrow!" 

They left eventually, leaving Tsuna with the older woman who checked on him a few more times before giving him a kiss on the forehead.

Tsuna smiled as he gently lay down, fedora still by his side. "Trouble does not seem to leave me....... Right, Reborn....." Tsuna's eyes glazed over with tears as the reality that his family and friends had died came crashing over him. He died too, but somehow ended up here. If whatever being sent him here, he hoped his family would also somehow be here, that they would be fine. 

Exhaustion piled on him as his eyes struggled to stay open, a small whimper leaving his lips as he drifts off. 

Recovery girl, hearing the whimper slowly made her way towards the door, opening it and stepping into the hallway. The others were still there, talking in hushed whispers as they conversed among themselves.

"He's asleep..." She interrupted their conversation.

"What'd you find?" Tsukauchi asked the older woman as they turned to her.

"He has scars.... A lot of them, some small ones no longer than a year old, the bigger ones probably obtained when he was in school....." Recovery girl grimly stated.

Silence encompassed them for a few second as they took in the information. 

"Abuse?......" Yagi reluctantly questioned.

"Let's not come to conclusions, we'll continue this tomorrow. Hopefully the students will keep to themselves and don't bombard the brunette with questions." Nedzu and Aizawa headed to the principal's office, Yagi and Tsukauchi heading their own way and Recovery girl heading back to the infirmary. 

Silently taking in the boy's soft features as he slept, she sat at her desk pulling a pen and some papers from the drawers and getting to work.

"This is going to be more work, isn't it?" Aizawa grumbled. Nedzu grinning at his post on the other's shoulder.

"More work indeed."


	2. Chapter 2

It was still dark outside when Tsuna woke up. A quick glance at a clock that hung on the wall confirmed it to be four in the morning.

Tsuna slowly got up, still a bit sore and groggy, but better than before.

He ran a hand through his hair as he pulled the blanket off of himself, before slowly getting up.

Looking around, he didn't spot Recovery Girl, but he did find clothes with a note on top that read, "Wear this, the thing on your body right now can't count for clothes. Either Yagi or Aizawa will come get you later in the morning. Recovery Girl."

Tsuna chuckled as he put down the note, then changed into the spare clothes the older woman left for him. A dark grey hoodie with matching sweatpants, orange sneakers that somehow fit and are the right size. An eyebrow rose as he put them on, amused that they got his shoe size while he was unconscious. Lastly, grabbing the fedora that lay on the bed, gently running his fingers through the hat's fabric before placing it on his head. The hat barely taming the wild spiky brown hair. 

"It's kind of incomplete without Leon....." Tsuna huffed.

A bit of awkward silence later, he decided to explore a bit, heading towards the door and silently opening it.

A long hall way greeted him, doors spaced evenly along one side, while large windows were situated at the other.

He walked to one of the large windows before peering over. "Hmmmmm, its huge...... Is the school government funded or just really rich?..." He muttered, a hand on his chin. He then gazed over the horizon, an unfamiliar sight of bright city lights greeted him. 

Tsuna sighed, "Well, sleep is not an option now. I better train then....... Reborn should be proud, goddammit." He grinned, lifting a hand and placing it on the fedora that sat on his head, the other hand reaching for the window's lock. Looking over his shoulder he whispered, "They wouldn't mind, would they?..."

He looked back to the window, his hand reaching for the lock, unlocking the window and opening it. Proceeding to jump out with a hand resting on the fedora to avoid it being blown away. Landing on the ground with a soft thud he crouched down, stretching his legs and arms. "Let's get this over with." He murmured before breaking out into a run a smile pulling at his lips.

It wasn't until a little over 6am that he got back, barely sweating, not even catching his breath, opening up the door that led to the infirmary only to be greeted by four pairs of eyes that stared at the brunette who awkwardly paused near the doorway.

Blinking, Tsuna awkwardly rubbed his nape, "I went for a run?....." The words coming out of his mouth like a question.

"Hah?..... HAH?!?!?!" Recovery girl came forward, her syringe like cane waving in the air as she stomped over to the guest. "A run?! In your condition?!?!!!" She grabbed the brunette by the arm, pulling him towards the bed and pushing him down onto the mattress. "What were you thinking?!? You were in grave conditions just yesterday and now you're running?!? You're going to give me more work if you don't stay still and let your body heal, brat!!" 

Recovery Girl pulled up the hoodie the other wore, her eyes searching for any indication the wound reopened, only to gape in surprise at the new scar where the wound was.

"My quirk should not have healed you this quickly........ It should still be just like it was just stitched after a surgery...." She ran her eyes over the wound before staring at the nervous brown eyes of the other, that darted from side to side, his gaze never falling on her.

"Care to explain, problem child?" Aizawa had his arms crossed over his chest, eyes glaring daggers at the brunette.

Tsuna frowned upon hearing the name the other called him, his gaze now fixated on the dark haired man. "I'm 31 thank you very much!" Tsuna smiled sarcastically as he thought, "Do I actually look that young?! I don't know if I should be offended or......"

"What?....." Detective Tsukauchi gaped, "He's the same age as Aizawa?!?!" Ran through his mind, his quirk not detecting any lies.

"The fu- We presumed you were in your early twenties at best!!" Yagi pointed a finger at the brunette, who now had his arms crossed as he pouted.

"Hmph!" Tsuna pouted even more, he knew he had somehow got his mother's immortal youth, but not by this much...... "No wonder Vongola always got underestimated when other Famiglia saw the Decimo....." He grumbled, not enough for the others to hear.

"With the way he's acting now, he might as well be the same age as my class.." Aizawa deadpanned, still not completely convinced of the brunette's actual age, and also in denial that they are the same age.

"Oh please no. I graduated highschool already, don't make me go back-" Tsuna backed away, shuddering at the memories he recalled back when he finally graduated middle school and moved onto highschool. "Reborn crammed three years worth of highschool academics in one year, with the remaining two years left drilling college level courses into my brain...literally......." Tsuna shudders at the recalled memory.

"That's what we're going to discuss next......but now knowing your real age......" Tsukauchi sighs, gesturing to all of them to follow as he walks out the infirmary on wobbly steps. The rest of them getting up and following silently, an unseen glint in Tsuna's eye and a small grin went unnoticed.

"I'm influenced by Reborn..." He shook his head as a gentle smile replaced the sadistic grin.

"I wonder if he's alright?...." Midoriya asked, worried for the guy who dropped out of the sky yesterday.

"Yeah, he was bleeding pretty badly..." Uraraka grimaced.

"His outfit also seemed to be in tatters!" Iida declared as his hand made choppy movements.

The topic of discussion among the students now centering around the occurrence yesterday.

The door opening with a loud bang startled the students as the room turned silent. Their eyes meeting their homeroom teacher's, as they hurriedly scurried to their seats.

Aizawa walks to the front accompanied by the guy who fell yesterday, earning gasps and mutters to spread around the room.

"Ok, this is Tsuna, he's your new home economics teacher, say hi." Aizawa then proceeded to take out a yellow sleeping bag, going to a corner before laying down, zipping it up, and turning away from the group of students. "I don't get paid enough for this."

Tsuna stared at the sleeping bag for a few more seconds before tearing his gaze away and to the students of the room, who stared at him with wide unblinking gazes before hands shot out.

Tsuna smiled before pointing to a girl with brown hair styled in a bob, cheeks rosy as her eyes glittered with curiosity. "Yes?" 

"Tsuna-sensei, why'd you fall out of the sky yesterday?" 

"Due to circumstances.... I'll now be teaching here for a while." He smiled before picking another student, a dark green haired boy who had symmetrical freckles dotted along his cheeks.

"Tsuna-sensei, what's your quirk?! I'm gonna assume its some sort of regeneration because you would not be up and about after a wound like that after just a couple hours, even with Recovery girl!" The student stated, his arm coming down from its outstretched pose as the student mumbled under his breath, his classmates, seemingly used to his antics, just ignored the barely audible mumbling, their focus on the brunette who stood blinking at the front.

Tsuna, having heard the mumbling, due to Reborn's tor-training, smiled in awe. "That's amazing how you can come up with infinite possibilities with merely a single look." 

The student flinched and stared at the teacher with embarrassment on his features.

"But, its sadly false, cause I don't have a quirk!" Tsuna gleefully declared as he grinned. The blinding smile making the students cover their eyes and shy away, but then registered his words.

"WHAT?!?!?!"


	3. Chapter 3

"What do you mean you don't have a quirk?!?!?!!" Yelling filled the room as the students expressed their disbelief.

"Exactly what I said." Tsuna smiled, a glint in his eyes as he took in the students expressions. "I don't have a quirk, because I'm not from here. I'm from another universe to be more precise! And due to a discussion with Nedzu-san, he proposed the idea of teaching in his school. Well, up until I figure out what I want to do on my own, since I can't exactly go back to my universe because of...circumstances, so I'm completely stuck here now!" He grinned even brighter.

"...........What?....." Momo spoke up, her eyes widening as she registered what this new teacher just said.

"HAH?!?!?!?" Bakugo had tiny explosions coming out of his hands, doubt clearly seen on his face.

Tsuna observed the tiny sparks, somehow reminded of a very familiar silverette. A small smile appearing as his thoughts drifted to his certain guardian. 

"Quirks are nonexistent in my universe and basically everyone is normal, apart from the people who live and come to Namimori for some reason." Tsuna grumbled and rolled his eyes on the last part. "So I'm quirkless, as you would call it here, however, in my universe, we do have another superpower, if you would call it that, but basically almost everyone doesn't know this power exists so its a minority." He continued as he paced, not paying any mind to the dumbstruck students, and the grumbling yellow worm.

"Different kinds, different uses, blah blah blah, just like quirks. I'm actually not supposed to tell anyone outside the people who know, but fuck the Vindice." The students noticed the brunette become more aggressive with his words, slowly backing away as they listened to the teacher's rant.

"This is a fucking different universe, the Omerta is fucking null! This is what they get for ADDING to my never ending PAPERWORK!!" Tsuna fumed, memories dancing in his mind. 

"I expected paperwork from my guardians, cause duh! I'm their boss! But for people outside my jurisdiction!?!?! What the fuck was Bermuda doing?!? Oh wait! He was a part of why I got more than a stack of fucking paperwork handed to me the next fucking day after their visit!!!! Even fucking Enma's guardians!! Like WHAT THE ACTUAL FUCK!! ON TOP OF THAT, EVEN THE FUCKING ARCOBALENO FOR CHRISTS SAKE! THEY'RE OLD NOW, FUCKING ANCIENT, RETURNED TO THEIR FORMER GLORY- BUT NOOOOOO!!!!! THEY HAVE TO MAKE ME DO THEIR WORK FOR THEM-" Tsuna paced back and forth in front of the room, an irritated expression marred his features.

The students blinking as the brunette ranted, mild curiosity on who this Enma person was, as well as the terms, 'guardian' and 'arcobaleno' was perceived from the onslaught of words. Although, wary glances were exchanged from the group as they returned their gazes at the grumbling teacher before them.

"Damn paperwork, should've just burnt it when I had the chance!" Aizawa silently agreeing to that statement.

"Fucking goddamn paperwork, fucking Reborn who won't give me a break, and I will never forgive you Lal Mirch for eating my cake-" Tsuna froze, his aggressive steps coming to a stop as his head turned to face the disturbed students.

Tsuna smiled, straitened his new suit, before speaking, "Where were we? Ah, yes! Me from another universe, yes, hello. A pleasure to meet all of you, I'll be your Home Economics teacher for a while. Call me Tsuna-sensei. Now any more questions?" 

The entire room was silent for who knows how long before Midoriya slowly raised his hand. "Yes?" Tsuna still smiling turned his attention to the freckled greenette. 

"I-if you don't h-have a qu-quirk, w-what's the power that your universe offers?...." The boy stuttered, his shoulders hunching in on himself as his gaze redirected to the floor.

Tsuna noticed the small gestures, his eyes slightly narrowing as he stared the the young teen.

"Its called 'Dying Will Flames', a high density form of energy that is refined through one's own life force, basically." The freckled teen perked up at the answer.

"There are fifteen flames in total, but two kinds, the Sky flame and the Earth flame, which has seven different attributes each, the last flame is rare, much rarer than the sky flame, but that's all I'm saying for now!" Tsuna clapped his hands together. "After all, it won't be fun if I just expose all my secrets now won't it?" Tsuna smirked, sending shivers down the students spine as they shuffled backwards a bit more, away from that.

"Well that's it for now! Its almost time for your next subject which is English? If I remember correctly. I'll see you all in the after noon!" Tsuna waved them goodbye and walked out the room, the bell signaling the end of homeroom, just ringing after the brunette stepped foot out into the hallway, Aizawa following after.

The class stood in shock at what just transpired. First they get introduced to a new teacher, that teacher being the one who fell out of the sky just yesterday! Next they find out that, that teacher is apparently from a different universe where quirks don't exist! But then the teacher tells them he has powers but its not a quirk. After going on a rant about everything, leaving them just in time for the next lesson.

"What the actual fuck?....."

Their stupefied demeanour only seemingly broken by the teacher who has come to teach the lesson. The students slowly dragging their feet as they returned to their seats.

Tsuna hummed a small tune as he and Aizawa walked down the hallway, to the teachers lounge where the teachers will hopefully stay until its time to leave, either for the next lesson they're assigned to, or for the day.

"Just went straight to the point there, didn't you." Aizawa grumbled stealing a glance at the brunette who twirled the fedora on his fingers.

"I mean, their reactions are quite interesting, wouldn't you say." Tsuna grinned as he faced his now fellow teacher, a smirk appearing on his lips after.

Aizawa smirked himself, tugging the scarf around his neck to hide his expression.

Tsuna chuckled, "And quite satisfying might I add." 

A thought swirled through Aizawa's head as he finds out something new about this brunette, "Devil incarnate." He huffed, body slacking as he thought about the trouble this new teacher will bring to the already troublesome life he lives.


	4. Chapter 4

The morning passed by quickly for the students of 1-A. Slightly out of it as they ate their lunches in the cafeteria, their thoughts still occupied by the strange, from another universe, now new teacher.

"What's up with all of you?" Shinsou raised an eyebrow as he stopped by the class' table, noticing their distant gazes and lack of noise.

"We got a new teacher apparently......" Kirishima scratched his cheek, an awkward air around him making the purple haired student raise his eyebrow even further.

"You mean Tsuna-sensei?" 

The class' gazes whipped to him in seconds, shock clearly visible on their faces.

"You know him?!" Kaminari raised his voice, pointing towards the Class 1-C student.

"Yeah, he just taught us, before lunch." Hitoshi grumbled, his tense shoulders relaxing a bit as he thought about the fedora wearing brunette teacher. "He's pretty cool......." He said softly before walking away.

"Yo.......he has known this teacher for maybe just an hour and he's going soft?!" Mina exclaimed, eyes wide as she stared at the retreating figure.

"That's......amazing honestly....." Momo expressed, amazed at how the new teacher got Shinsou to open up. 

"I'm kind of looking forward to the lesson!" Midoriya exclaimed, a shine in his eyes as questions swirled around in his mind. 

"Same here!" Agreement's came from most of the others.

"Heh! For the class that's supposed to be top of the top, you get introduced to the new teacher last!" Monoma sneered as he and some other class 1-B students stopped by the group of 1-A.

Itsuka slapped him across the back of his head, "Stop that! Don't get salty just because you don't have Tsuna-sensei's attention for the mean time!" She scolded the blonde.

Said blonde erupted into a pink blushing mess, "Shut up!" He stomped away, a scowl on his lips betrayed by the pink tints in his cheeks and ears.

"Sorry bout him, he somehow got attached......but to be honest, everyone probably got attached." She laughed before giving a final wave toward the 1-A group before she followed after the fuming blonde, the others on her tail after giving a nod.

"Monoma too?!?!" Uraraka brought up a hand to her mouth, perplexed by the other class' reactions.

"Now I'm kinda scared...." Jirou nervously chuckled. What did the new teacher do to make even Monoma for Christ's sake, adore him?!

"You don't think he lied and didn't tell anyone that he actually has a quirk that makes everyone adore him, do you?" Kirishima questioned warily.

"I'll fucking beat him to a pulp if he tries anything!!" Bakugo's hands erupted into small explosions, the ever present scowl more prominent.

"Nonsense!! Tsuna-sensei is probably merely a great teacher..." Iida exclaimed, although his voice becomes softer towards the end, laced with uncertainty and his hand chopping movements slowly stopped.

"Ahaha.........." 

Lunch somehow passed by really quickly for 1-A. Their steps getting slower as they neared their classroom. Nervous, and slightly dreading entering. 

Iida took a deep breath before sliding the door open, expecting getting hit by a quirk, a scolding for being a few minutes late, or even a villain ambush! But not this........ 

He and the others in front who got a view of the room froze, their eyes going wide.

"Why'd you guys stop? Kero." Asui questioned before leaning forward to get a view.

Bakugo clickled his tongue, before barreling through his fellow classmates, shoving them aside as he entered the room. "What the fuck?....." His shocked gaze swept over the entire room before stopping at the teachers desk in front. Where Tsuna sat, a tablet in hand and a steaming cup of espresso sat on the desk. He scrolled through a few more times before taking the espresso filled cup, took a sip and placed it back on the saucer.

"Three minutes and forty five seconds late, oh dear." Tsuna faced his class, a small smile on his lips. "Being late is never a good thing if you're planning on becoming heroes. Let us work on that, Yes?" Tsuna put the tablet down on the desk as he got up.

"Now let's get started on Home Economics! Our topic for today is baking! I was going to give you guys a treat since its our first lesson, but now........" Tsuna's gaze swept over his frozen students. "Consider it as a penalty for being late."

Tsuna went to one side of the blackboard, before flipping it. Now a whiteboard in its place with beautifully elegant hand writing.....

"We're going to be baking chocolate chip cookies! Get your aprons and let's get started!"

Class with Tsuna-sensei was interesting, to say the least. He somehow transformed the entire classroom into a bakery.....

Oven's, stoves, kitchen ware and baking utensils we're there instead of their desks and chairs. How the brunette got all of this equipment in here, no one knows.

After splitting up into small groups, the teens got to work on making cookies. Taking out ingredients, dumping them into bowls, mixing, as they occasionally glanced up to the whiteboard where detailed and easy to understand instructions were written.

"I did not know our blackboard could flip like that..." Uraraka started the conversation, glancing toward the front before looking back at Midoriya who cracked a few eggs into a bowl. 

"Neither did I." A voice answered from the door, the students looking up and meeting the exhausted and slightly surprised gaze of their homeroom teacher.

Aizawa raised a brow at the brunette, who answered with a bright smile, "I got permission from Nedzu-san!"

"Where'd you even get the amount of money to buy all of this? The schools budget wasn't dented." 

Tsuna grinned, a predatory gaze aimed at his fellow teacher, who shivered under the stare. "You really want to know?" 

"No. Forget I ever asked." Aizawa deadpanned before slamming the door and walking away.

Tsuna chuckled before going back to his students, who awkwardly mixed ingredients. "If you guys finish before the time for this subject is over, I'm making everyone a little something!"

When Present Mic entered for the next lesson, the classroom was back to normal by then, with a click of a button by Tsuna. The Voice Hero was greeted by a class sipping on milkshakes and frappes, accompanied by chocolate chip cookies. He blinked before his gaze landed on the teacher's desk, where a plate of cookies and a cup of shake sat. He headed for the desk, noticing a small note beside the snacks. Picking it up and reading over it, he laughed. "No wonder Shouta got along with him and Nedzu was esctatic!" 

He picked up a cookie and took a bite. His eyes widened slightly at the taste before taking another. "Alright, finish it up and we'll start class!"

The students who held their breath as their teacher took a bite of the cookie, beamed as they got permission to eat the rest of the snacks. "Yes!!"

**Notes for the Chapter:**

> Lol  
> I'm having fun with this-  
> Reborn taught Tsuna well, a little too well-  
> If Tsuna ever pulls out anything, its better to just not ask where he got it. The skill? He got from Reborn. The item? Probably through illegal means, but no one has to know.


	5. Chapter 5

A whole week went by as Tsuna taught at UA. The students, as well as teachers, regarded the brunette highly.

He is a topic of conversation for everyone in the school, including the older students. Mostly because of his teaching skills but also because of his personality that he was liked by everyone. 

Immeasurable kindness and patience, his presence wrapping over you like a warm blanket, making tense shoulders relax, and keeping you calm.

Every class he taught, he impacted quite well. Teaching each individual student different ways that benefitted said student. He slowed down his lectures for the students who needed time to catch up, he gave the more knowledgeable students harder quizzes and tests. Each test or quiz made specifically for each individual student. 

He also prioritized subjects that students may be quite lacking in, but did not undermine the other subjects as well.

It was balanced and the students we're learning easier each day. 

"Tsuna-sensei made me want to actually do math..."

"Tsuna-sensei made me memorise kanji."

"I actually learned how to Science and Biology."

"I now have more recipes to add to the restaurant I plan on opening after highschool."

"I also found out more uses for my quirk. Did not know hydrogen peroxide could be used as antiseptic or mouth wash-"

"Isn't he teaching Home Economics though....... How the hell does he know so much?......"

Theories spread on how the brunette teacher has so much knowledge on basically everything. "Is he as smart as Principal Nedzu?!" Was a question students asked each other often, although no one actually knew the answer. 

It wasn't until Tsuna found himself in the cafeteria one day, did a few courageous students walk up to him.

"Tsuna-sensei!!!" They waved at the fedora wearing brunette before jogging to where he was.

Three students, second years Tsuna noticed as he glanced at their uniforms, stopped in front of him.

"Yes?" He smiled.

"There are theories going around on how you obtained your knowledge and we wanted to know the answer!!" The student had sparkling eyes as she gazed at the teacher.

At her outburst, the entire cafeteria seemingly became more quiet as most of the students perked up, now staring at the brunette, some more subtle as they continued to nibble on their lunches, but keeping their attention on the conversation.

Tsuna smiled amusedly, "I had a tutor come into my life when I was in middle school. He drilled it all into my brain....literally..." He grimaced and suppressed a shudder, although the students could see a small fond smile tugging at his lips. "He was the incarnation of Satan I tell you! When I got the answer to a question wrong he would trigger a bomb! How my room or house lived, I have no idea!" He threw his arms up in exaggeration, keeping an eye on the slightly terrified expressions of the students.

"A what?......."

"Explosives! The old ones used back in war with the detonator that you push down. Explosions became a common occurrence, no one bats an eye toward it anymore." He chuckled. "Ooh, let's not forget about training! He would set up traps around the neighborhood, make me go through said traps, while running away from angered dogs, with said tutor firing bullets at my feet. If I slowed down even a smidge, I would have been mauled and had bullet holes all throughout my body!" He grinned.

His gaze swept across the now silent cafeteria, a smirk on his lips. "I'm kidding!"

Moments of silence followed, the students barely registering what they just heard. 

"Tsuna-sensei! No fair!! We want the truth!!" Students whined as tense shoulders relaxed.

Tsuna barked a laugh, some students laughing along with him and others sporting smiles.

"Theories are welcome." He winked before sweeping his gaze across the large room full of students, stopping at the curly mop of green hair he recognized.

"Midoriya-kun!" Tsuna waved.

The greenette flinching at the sudden attention he was getting, his nervous eyes staring at the teacher.

"Meet me after lunch, okay?" Tsuna grinned before saying his goodbyes to the students and headed out the cafeteria, likely going to the principal's office, he seems to frequent there a lot. Most of the teachers terrified as the brunette and the mouse spent hours together, the brunette having a bright smile on his face as he walks out of the office, the white rat grinning sadistically, spiky teeth bared if anyone peeked in after Tsuna.

Those who saw, shivered and trembled as they hurriedly got away from the room. 

"What did you want with Midoriya-kun, Tsuna-kun?" Nedzu asked as he sipped on his tea, pages sprawled out at the table in front of him.

"Nothing much, just MC business." Tsuna shrugged as he sat opposite the principal, taking off the fedora on his head and placing it on the empty spot on the table, where papers didn't reach.

Nedzu hummed, a smirk on his lips.

Tsuna chuckled, before picking up a paper from the table he leaned back and looked over it. 

"Just MC business indeed."

**Notes for the Chapter:**

> My inspiration for teacher Tsuna is Koro-sensei! I imagine him actually taking the time of the day to teach each student individually if he could, but settled for making small adjustments.
> 
> Also, is he actually kidding?! Only viewers know😌
> 
> Tsuna and Nedzu cooking something up and it ain't breakfast, lunch or dinner-
> 
> Run-
> 
> Also breaking the fourth wall is a must🙄


	6. Chapter 6

"Problem children, you've got a training exercise coming up in a few days, be ready." Aizawa announced and headed to a corner of the room, pulling out a yellow sleeping bag and curling up away from the class.

It was quiet for a few seconds before murmurs spread quickly throughout the room.

"A training exercise?! I wonder where we'll go?" Mina bounced as she stood up.

"Hopefully not in the USJ...... Still gives me nightmares....." Kaminari shivered and earns nods of agreement.

"Somewhere new would be cool! Like maybe in another district?" Uraraka exclaimed clapping her hands together.

"What if we just end up here at school?..." 

"Well, t-the school i-is pretty big. So m-maybe there's a se-section we haven't been to y-yet?..." Midoriya stammered out, slightly squeaking at the attention that turned to him.

"Maybe, but it would be awesome if we went somewhere else!"

"Here's a cross stitch. A Cross-stitch is a form of sewing and a popular form of counted-thread embroidery in which X-shaped stitches in a tiled, raster-like pattern are used to form a picture." Tsuna explained as he drew on the board.

"Its the oldest form of embroidery and can be found all over the world since the middle ages." He continued to draw detailed fabric with the stitches somehow symmetrical and the same in size.

"Why the fuck are we even learning this shit?! This is useless to teach hero students!!" Bakugo slammed his palms on the desk, glaring at the teacher.

The other students grimaced at the blonde, but slightly agreed to the statement. Although a few others were lost in thought about the topic, Tsuna noted them and nodded.

"What happens if you need to do a DIY repair in the middle of a fight? If a specific part of your clothes are in dire need of repair and you need that part to effectively use your quirks or are immobile until that part is fixed?" Tsuna questioned, eyes sweeping over the students as realization settled in. 

"But sewing mid-fight is impossible!" Iida exclaimed.

Tsuna smiled before reaching up and tearing the black vest he wore at the shoulder seam.

"Wha-?!?!" 

The fabric dangled, flapping slightly as the brunnete moved. 

"This could easily get caught if I'm fighting a villain close range. Even long range attacks like fire may damage it and spread throughout my body. Easy fix would be to discard it, but what if I had support gear stuffed in my pockets on the vest? If I had medical supplies attached and first aid is needed, if I discard it, the one I'm fighting would destroy it if he saw what its contents are." Tsuna swept over the students contemplating expressions a smile on his face.

"Which is why you want to be ready for anything that may happen when on the job. You might want to have medical supplies with you in case you encounter a victim that needs immediate treatment while you wait for the ambulance, or a sewing kit for fixing up your suits for the mean time or for fixing human flesh." That made the students flinch as they stared up at their teacher.

"Sewing can be used for many things, patching up your clothes, adding to your clothes, or the needles could be used as an emergency weapon." Tsuna listed down, his students expressions slowly turning into disbelief and teetering on the edge of terrified. "If a wound is in dire need of a suture, a temporary fix could be applied by you who is on site until the medics arrive!"

The class was in silence as they stared warily at the brunette who picked up a needle and black thread out of a sewing kit that lay on the teacher's desk. "If you get good enough...." He threaded the needle and held it up. "You could finish in seconds!" He quickly grabbed the fabric, holding the two pieces together and sewing. The action far too fast for the students to see, merely staring in shock as the teacher finished it off and cut the excess thread.

The vest looking brand new, the tear nowhere to be seen. 

Tsuna smiled brightly as he turned back toward the board, picking up the discarded chalk he continued the lesson, feeling the students gazes on him the entire time.

"Tsuna-kun, did you know the two heroics classes are going on a joint training session?" Nedzu asked as he sipped on tea, sitting on a couch in his office.

The brunette sitting opposite sipping on his own cup.

He put it down and hummed, "Is that so? Would you allow me to go too, Principal?" 

"Oho, and why would you want to go?" Nedzu asked, intrigued at the brunette asking for permission.

"I'm quite curious on how hero students train. And also, my intuition tells me I should go." Tsuna resumed sipping on tea.

"I see. Very well then, tell me all about it when you get back?"

"Of course." A grin was exchanged between the two.

**Notes for the Chapter:**

> Can someone tell me how to put in pictures?😅 I want to draw teacher Tsuna with the students! And I want you guys to see it!
> 
> I just don't know how others put fanart or their own drawings in here😭 I need to fiddle with this site-
> 
> Also, my knowledge comes from google so if something is off, I did not research it enough, and my knowledge is lacking in that department so tell me and I shall fix it😌
> 
> Also thank you on the support I've been getting I'm glad you like this sudden impromptu story.


End file.
